Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$202.41	13.369%	$229.4702	$229.47	$229.45	$229.50
Purchase #2	$162.53	5.753%	$171.8804	$171.88	$171.90	$171.90
Purchase #3	$82.57	13.321%	$93.5691	$93.57	$93.55	$93.60
Purchase #4	$130.42	10.319%	$143.878	$143.88	$143.90	$143.90
Purchase #5	$59.74	9.872%	$65.6375	$65.64	$65.65	$65.60
Purchase #6	$228.25	3.154%	$235.449	$235.45	$235.45	$235.40
Purchase #7	$72.94	11.653%	$81.4397	$81.44	$81.45	$81.40
7 purchase totals =	$938.86		$1,021.3239	$1,021.33	$1,021.35	$1,021.30